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The December 2018 M (sub L) 5.7 and January 2019 M (sub L) 5.3 earthquakes in South Sichuan Basin induced by shale gas hydraulic fracturing

Xinglin Lei, Zhiwei Wang and Su Jinrong
The December 2018 M (sub L) 5.7 and January 2019 M (sub L) 5.3 earthquakes in South Sichuan Basin induced by shale gas hydraulic fracturing
Seismological Research Letters (April 2019) 90 (3): 1099-1110

Abstract

An M (sub L) 5.7 earthquake struck Xingwen County, Sichuan Province, China (28.239 degrees N, 104.922 degrees E) on 16 December 2018. More than two weeks later on 3 January 2019, an M (sub L) 5.3 earthquake occurred 8 km to the west. These were the largest and most damaging events in the Changning shale gas block and resulted in extensive damage to nearby farmhouses and other structures. Although the official hypocentral depths for both events are large than 5 km, the centroid moment tensor solutions based on the generated cut-and-paste method were very shallow (3 and 1.8 km for M (sub L) 5.7 and 5.3, respectively). In addition, both events were very close to hydraulic-fracturing (HF) zones of horizontal wells, in which HF was ongoing. A convening chain of evidence, including spatiotemporal correlation between earthquakes and HF zones, statistic parameters of seismicity, and estimated overpressure required to activate the unfavorably oriented source faults of the largest events, suggests that a series of earthquakes were induced by HF at a depth of approximately 2.5-3 km. In the Changning block, thus far, 11 M (sub L) > or =4.0 events (including 3 M (sub L) > or =5.0) were observed since the systematic HF operation began in 2014. The Omori-type aftershock productivity is very low as compared to normal tectonic seismicity. In addition, estimated overpressure ranged from approximately 0.3 to 5.8 MPa for M (sub w) >3.5 events. The poroelastic stress changes are less than 1 MPa out of the treatment zones. Hence, overpressure-driven reactivation of pre-existing faults (most of them are unmapped and unfavorably oriented for slip under the present tectonic stress field) is considered to be the cause of these abnormal moderate-size earthquakes.


ISSN: 0895-0695
EISSN: 1938-2057
Serial Title: Seismological Research Letters
Serial Volume: 90
Serial Issue: 3
Title: The December 2018 M (sub L) 5.7 and January 2019 M (sub L) 5.3 earthquakes in South Sichuan Basin induced by shale gas hydraulic fracturing
Affiliation: Japanese Geological Survey, Ibaraki, Japan
Pages: 1099-1110
Published: 20190403
Text Language: English
Publisher: Seismological Society of America, El Cerrito, CA, United States
References: 35
Accession Number: 2019-032196
Categories: SeismologyEconomic geology, geology of energy sources
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch maps
N28°00'00" - N28°30'00", E104°45'00" - E105°00'00"
Secondary Affiliation: Earthquake Monitoring Centre, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201917
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